Explosives are substances that possess large quantity of potential, or stored, energy, which can rapidly release to generate an explosion. An explosion is generally the result of a spontaneous chemical reaction which rapidly releases the chemical energy stored in the explosive material in the form of heat, pressure, sound, and light.
History of Explosives
Explosives throughout history have been used for a variety of uses. These uses include recreation, mining, weaponry, and demolition. The earliest recorded use of explosives comes in the 10th century, in China, where they were used for both fireworks and signaling. Throughout the medieval ages however, explosives were utilized in weaponry, mostly in the form of cannons, and early firearms. For centuries afterward, explosives were generally used in the form of weaponry, until the early 20th century, when more applications were discovered. [1][2]
Applications of Explosives
Since they were first discovered around a thousand years ago, people have utilized explosives for a number of things, ranging from recreation, to blast mining, to high powered military weaponry.
Recreation
Explosives, in the form of fireworks, are often used to entertain large crowds of people. They are known for their amazing displays of light in different shapes in color. The varieties and colors are determined by chemical composition of explosive component of the firework. Fireworks are one of the most common forms of explosives available today. [3]
Blast Mining
In mining, explosives are often used to make mining minerals easier. This is often used in coal mining to loosen the rock and coal. On surface deposits, holes are drilled and filled with explosives at specifically determined locations then set off, shattering the rock and coal in the area. In underground deposits, the same method is often used. After the rocks are broken up, it is easier to extract the coal, which is then done.[4]
Demolition
In demolition, explosives are often used to quickly bring down old structures quickly and efficiently, with only a small amount of explosives. Explosive charges are strategically placed in the building, generally near support beams, to create just enough explosive power to bring down the structure in a controlled and safe manner. The debris is then cleared up by bulldozers and workers.[5]
Military Weaponry
Explosives have been used in war since medieval times. They have a wide range of military use, ranging from small firearms
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, to devastating nuclear weapons. Almost all military weapons now utilize explosives in some form or another, as they are generally incredibly destructive and deadly. Firearms, for example, use explosives to propel bullets at high velocities.[6]
Types of Explosives
All explosions are caused by a chemical decomposition in explosive material. The chemical structure of explosives often contain high amounts of energy, which, when the structures are decomposed, release that energy in the many forms we see from explosions. Explosives are often classified by how they decompose and release their potential energy to create the explosion. They generally are split into 3 broad categories, Deflagration, Detonation, and Exotic. [7]
Deflagration
Deflagration explosives, also known as low explosives, burn using heat to trigger decomposition. In such an explosive, when triggered a flame front slowly moves through the material, usually at velocities lower then the speed of sound, setting it off once ignited. As a result, they produce a much slower explosion then the other types of explosives, which in turn cause a much less powerful explosion, in comparison to others. Fireworks are generally deflagration explosives.
Detonation explosives, also known as high explosives, produce much larger explosions. They are characterized by a much more rapid decomposition. In detonation explosives, the explosion is caused by shock, which travels through the material in the form of a shock wave. These shock waves travel at a high rate of speed, usually in the range of several thousand meters per second, much faster then deflagration. This generates a much faster and abrupt decomposition, releasing potential energy at a much faster rate, resulting in a much larger explosion. Because of this property, much of the explosives used in demolition, mining, and weaponry are detonation explosives. [10]
Exotic
Unlike the other two types, Exotic explosives do not result from chemical decomposition. They instead result from other phenomena, depending on the material. One such example of exotic explosives is the nuclear explosive. This type of explosion utilizes either fission or fusion reactions on the sub-atomic level. This form of explosion, which is what at fuels stars, such as our very own sun, to create the vast amounts of energy they release in the form of light and heat.
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Nuclear explosives have also been used to create devastating bombs with enough power to destroy whole cities with one bomb. Several other types of exotic explosives exist, such as the theoretically described matter-antimatter annihilation, where normal matter, and its theoretical antimatter counterpart, collide, causing a massive release of energy and annihilation of the particle. Many other types of exotic explosives exist, but they are very rare and fairly difficult to control. They are not generally used, except in rare and extreme situations as a result. [11]
Main properties of explosives
Explosives have several properties that influence the explosion it creates, most of which are determined by its chemical structure.
Material Composition
Explosive materials are generally either a purely chemical compound, or a mixture of a source of oxidation and fuel. Explosives in the form of pure chemical compounds are generally unstable, and sensitive to certain forms of stimulus, such as shock or heat. Once stimulated, these compounds generally react by separating and changing into gases. The rapid release of gas and energy from the reaction then expands at very fast speeds, generating an explosion. These are generally referred to as high explosives. Explosions resulting from oxidation and fuel combination are much different. In this material, the explosion is triggered by combustion of the fuel. The burning of the fuel then results in the rapid release of gases and energy, generating an explosion. These explosions are generally referred to as low explosives. However,whether high or low, most explosives generate an explosion as the result of chemical reactions. All explosive chemical reactions must involve four key properties to be considered an explosive. The reaction must be very rapid, include the formation of gases, release large amounts of energy in the form of heat, and be triggered by shock or heat. [12]
Stability
The stability of explosive is its ability to be stored without deteriorating into a non-explosive state. This property is very important because it determines whether it is safe to store, and if so, in what conditions. Several factors contribute to stability:
Chemical Structure -- The chemical structure of the material greatly influences its stability. The structure determines how quick the material is to decompose under certain conditions. For example, certain compounds are much more susceptible to heat then others, as a result of its structure. Compounds, such as nitrites, nitrates, and azides, for example are intrinsically unstable, and commonly found in explosives. [13] Temperature of Storage -- Temperature greatly effects stability as well. In all explosives, as temperature rises, so too does the rate of decomposition. So, explosives are better stored in cooler areas. This is especially important, as some explosives are so sensitive to temperature, that they are triggered even by average room temperature. Sun exposure-- Some compounds are sensitive to ultraviolet rays from the sun, such ones that contain nitrogen. Exposure in some cases can trigger an explosion, meaning that this must be taken into consideration. Electrical discharge -- Many compounds can be triggered by electrical discharges, causing detonation. Therefore storage and handling of such explosives must take this into consideration. [14]
Power
Perhaps the most important aspect to an explosive is its power. In physics, power is simply the ability of something to do work, that is, the ability to move things by force across a certain distance. So, the more powerful something is the more effective it is at moving things, at a faster rate. There are several things that power is affected, as well as measured, in explosives. Generally, because it is difficult to measure the exact potential energy that explosive compounds contain, without physical testing of explosives, their power cannot be effectively determined. So, there is a series of tests that are applied to explosives to determine its explosive power. These tests generally involve taking a small, controlled amount of the explosive, detonating them, and recording data based on the tests. The most common of the tests, the Cylinder expansion test, is used for just about all explosives, while the many others are more specific based on application. In the Cylinder Expansion Test, a pre-determined amount of the explosive is placed in a long hollow tube. Then, the material is detonated, and data is collected and analyzed about the distance and rate of expansion to determine the velocities generated by the explosion. This velocity is also known as the explosives Gurney energy, which is a constant unique to each explosive, and is generally displayed in units as millimeters per microsecond, or m/ms, although it is also the equivalent of km/s, a much more familiar unit with easier application. This is used to compare the effectiveness of explosives relative to others, which is very useful in determining which type of explosive and chemicals are best for the situation. [15][16]
Brisance
Describes the ability of an explosive to fragment, generally referring to the casing that holds the explosive material together. This generally only applies to smaller explosives, such as hand grenades, where the breaking and shattering is the desired effect.[17]
Hygroscopicity
This is a measurement of the effect that water has on the overall effectiveness of the explosive. This is generally a measure of how much moisture the substances in the explosive material absorb. Water generally reduces important aspects of an explosive, including is strength and sensitivity, because when vaporized in an explosion, it has a cooling effect on the surrounding gases, reducing its energy and power output.[18]
Toxicity
Most explosives, due to their unstable chemical nature, are toxic. It is important to note this when storing and retrieving explosives. The gases released in explosions are sometimes toxic as well.[19]
Energy of Explosions
When an explosive is triggered, massive amounts of energy are released in a short amount of time. This energy is released in several forms, including heat, sound, light, and high pressures.
Heat
During an explosion, a large amount of heat is generated, this is because of the rapid decomposition of chemical bonds and structure between molecules in the explosive material. When dissolved, these bonds release all of the energy holding it together, mostly in the form of heat, which in turn decreases the stability of more molecules around it. This then triggers more decomposition which soon triggers decomposition throughout the whole material. This all occurs in a fraction of a second. This rapid increase of energy and heat raises temperatures to very high levels, anywhere from several thousand degrees Fahrenheit in most explosives like TNT, to several million degrees in atomic bombs. These immense temperature causes all of the explosive material’s mass to change into a gas, since no solid can exist at such high temperatures. [20]
Pressure
As a result of the high density of gases formed, an area of relatively huge pressure is formed, which, because they are gases, expand rapidly at velocities up to, and higher then 1000m/s. The rapidly expanding gases form what is called a blast wave, which is an expanding wave of energy from the explosion. Followed by it is generally a high pressure wave of gases, and in some cases, secondary waves, which depends on the type of explosive, and total mass. The pressure waves, in the form of shock waves, is generally what causes most of the damage resulting from most explosions
The sound in generally caused by changes in pressure. Since an explosion causes a dramatic shift in pressures in the immediate area of the explosion, a normally loud sound is produced.
Table of Contents
Explosives
Explosives are substances that possess large quantity of potential, or stored, energy, which can rapidly release to generate an explosion. An explosion is generally the result of a spontaneous chemical reaction which rapidly releases the chemical energy stored in the explosive material in the form of heat, pressure, sound, and light.
History of Explosives
Explosives throughout history have been used for a variety of uses. These uses include recreation, mining, weaponry, and demolition. The earliest recorded use of explosives comes in the 10th century, in China, where they were used for both fireworks and signaling. Throughout the medieval ages however, explosives were utilized in weaponry, mostly in the form of cannons, and early firearms. For centuries afterward, explosives were generally used in the form of weaponry, until the early 20th century, when more applications were discovered. [1] [2]
Applications of Explosives
Since they were first discovered around a thousand years ago, people have utilized explosives for a number of things, ranging from recreation, to blast mining, to high powered military weaponry.
Recreation
Explosives, in the form of fireworks, are often used to entertain large crowds of people. They are known for their amazing displays of light in different shapes in color. The varieties and colors are determined by chemical composition of explosive component of the firework. Fireworks are one of the most common forms of explosives available today. [3]
Blast Mining
In mining, explosives are often used to make mining minerals easier. This is often used in coal mining to loosen the rock and coal. On surface deposits, holes are drilled and filled with explosives at specifically determined locations then set off, shattering the rock and coal in the area. In underground deposits, the same method is often used. After the rocks are broken up, it is easier to extract the coal, which is then done.[4]
Demolition
In demolition, explosives are often used to quickly bring down old structures quickly and efficiently, with only a small amount of explosives. Explosive charges are strategically placed in the building, generally near support beams, to create just enough explosive power to bring down the structure in a controlled and safe manner. The debris is then cleared up by bulldozers and workers.[5]
Military Weaponry
Explosives have been used in war since medieval times. They have a wide range of military use, ranging from small firearms
Types of Explosives
All explosions are caused by a chemical decomposition in explosive material. The chemical structure of explosives often contain high amounts of energy, which, when the structures are decomposed, release that energy in the many forms we see from explosions. Explosives are often classified by how they decompose and release their potential energy to create the explosion. They generally are split into 3 broad categories, Deflagration, Detonation, and Exotic. [7]
Deflagration
Deflagration explosives, also known as low explosives, burn using heat to trigger decomposition. In such an explosive, when triggered a flame front slowly moves through the material, usually at velocities lower then the speed of sound, setting it off once ignited. As a result, they produce a much slower explosion then the other types of explosives, which in turn cause a much less powerful explosion, in comparison to others. Fireworks are generally deflagration explosives.
[8] [9]
Detonation
Detonation explosives, also known as high explosives, produce much larger explosions. They are characterized by a much more rapid decomposition. In detonation explosives, the explosion is caused by shock, which travels through the material in the form of a shock wave. These shock waves travel at a high rate of speed, usually in the range of several thousand meters per second, much faster then deflagration. This generates a much faster and abrupt decomposition, releasing potential energy at a much faster rate, resulting in a much larger explosion. Because of this property, much of the explosives used in demolition, mining, and weaponry are detonation explosives. [10]
Exotic
Unlike the other two types, Exotic explosives do not result from chemical decomposition. They instead result from other phenomena, depending on the material. One such example of exotic explosives is the nuclear explosive. This type of explosion utilizes either fission or fusion reactions on the sub-atomic level. This form of explosion, which is what at fuels stars, such as our very own sun, to create the vast amounts of energy they release in the form of light and heat.
Main properties of explosives
Explosives have several properties that influence the explosion it creates, most of which are determined by its chemical structure.
Material Composition
Explosive materials are generally either a purely chemical compound, or a mixture of a source of oxidation and fuel. Explosives in the form of pure chemical compounds are generally unstable, and sensitive to certain forms of stimulus, such as shock or heat. Once stimulated, these compounds generally react by separating and changing into gases. The rapid release of gas and energy from the reaction then expands at very fast speeds, generating an explosion. These are generally referred to as high explosives. Explosions resulting from oxidation and fuel combination are much different. In this material, the explosion is triggered by combustion of the fuel. The burning of the fuel then results in the rapid release of gases and energy, generating an explosion. These explosions are generally referred to as low explosives. However,whether high or low, most explosives generate an explosion as the result of chemical reactions. All explosive chemical reactions must involve four key properties to be considered an explosive. The reaction must be very rapid, include the formation of gases, release large amounts of energy in the form of heat, and be triggered by shock or heat. [12]
Stability
The stability of explosive is its ability to be stored without deteriorating into a non-explosive state. This property is very important because it determines whether it is safe to store, and if so, in what conditions. Several factors contribute to stability:
Chemical Structure -- The chemical structure of the material greatly influences its stability. The structure determines how quick the material is to decompose under certain conditions. For example, certain compounds are much more susceptible to heat then others, as a result of its structure. Compounds, such as nitrites, nitrates, and azides, for example are intrinsically unstable, and commonly found in explosives. [13]
Temperature of Storage -- Temperature greatly effects stability as well. In all explosives, as temperature rises, so too does the rate of decomposition. So, explosives are better stored in cooler areas. This is especially important, as some explosives are so sensitive to temperature, that they are triggered even by average room temperature.
Sun exposure-- Some compounds are sensitive to ultraviolet rays from the sun, such ones that contain nitrogen. Exposure in some cases can trigger an explosion, meaning that this must be taken into consideration.
Electrical discharge -- Many compounds can be triggered by electrical discharges, causing detonation. Therefore storage and handling of such explosives must take this into consideration.
[14]
Power
Perhaps the most important aspect to an explosive is its power. In physics, power is simply the ability of something to do work, that is, the ability to move things by force across a certain distance. So, the more powerful something is the more effective it is at moving things, at a faster rate. There are several things that power is affected, as well as measured, in explosives. Generally, because it is difficult to measure the exact potential energy that explosive compounds contain, without physical testing of explosives, their power cannot be effectively determined. So, there is a series of tests that are applied to explosives to determine its explosive power. These tests generally involve taking a small, controlled amount of the explosive, detonating them, and recording data based on the tests. The most common of the tests, the Cylinder expansion test, is used for just about all explosives, while the many others are more specific based on application. In the Cylinder Expansion Test, a pre-determined amount of the explosive is placed in a long hollow tube. Then, the material is detonated, and data is collected and analyzed about the distance and rate of expansion to determine the velocities generated by the explosion. This velocity is also known as the explosives Gurney energy, which is a constant unique to each explosive, and is generally displayed in units as millimeters per microsecond, or m/ms, although it is also the equivalent of km/s, a much more familiar unit with easier application. This is used to compare the effectiveness of explosives relative to others, which is very useful in determining which type of explosive and chemicals are best for the situation. [15] [16]
Brisance
Describes the ability of an explosive to fragment, generally referring to the casing that holds the explosive material together. This generally only applies to smaller explosives, such as hand grenades, where the breaking and shattering is the desired effect.[17]
Hygroscopicity
This is a measurement of the effect that water has on the overall effectiveness of the explosive. This is generally a measure of how much moisture the substances in the explosive material absorb. Water generally reduces important aspects of an explosive, including is strength and sensitivity, because when vaporized in an explosion, it has a cooling effect on the surrounding gases, reducing its energy and power output.[18]
Toxicity
Most explosives, due to their unstable chemical nature, are toxic. It is important to note this when storing and retrieving explosives. The gases released in explosions are sometimes toxic as well.[19]
Energy of Explosions
When an explosive is triggered, massive amounts of energy are released in a short amount of time. This energy is released in several forms, including heat, sound, light, and high pressures.
Heat
During an explosion, a large amount of heat is generated, this is because of the rapid decomposition of chemical bonds and structure between molecules in the explosive material. When dissolved, these bonds release all of the energy holding it together, mostly in the form of heat, which in turn decreases the stability of more molecules around it. This then triggers more decomposition which soon triggers decomposition throughout the whole material. This all occurs in a fraction of a second. This rapid increase of energy and heat raises temperatures to very high levels, anywhere from several thousand degrees Fahrenheit in most explosives like TNT, to several million degrees in atomic bombs. These immense temperature causes all of the explosive material’s mass to change into a gas, since no solid can exist at such high temperatures. [20]
Pressure
As a result of the high density of gases formed, an area of relatively huge pressure is formed, which, because they are gases, expand rapidly at velocities up to, and higher then 1000m/s. The rapidly expanding gases form what is called a blast wave, which is an expanding wave of energy from the explosion. Followed by it is generally a high pressure wave of gases, and in some cases, secondary waves, which depends on the type of explosive, and total mass. The pressure waves, in the form of shock waves, is generally what causes most of the damage resulting from most explosions
Sound
The sound in generally caused by changes in pressure. Since an explosion causes a dramatic shift in pressures in the immediate area of the explosion, a normally loud sound is produced.
Slideshow and Animation
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